Water heater



Dec. 20, 1966 A. MILLER ETAL WATER HEATER Filed Sept. 28, 1964 y 5. m? J M MIMWW 4 Z M 2 United States Patent Ofltice 3,292,598 Patented Dec. 20, 1966 3,292,598 WATER HEATER Avy L. Miller, 13246 Saticoy St., North Hollywood Calif. 91605, and Robert M. Ramey, North Hollywood, Calif; said Ramey assignor to said Miller.

Filed Sept. 28, 1964, Ser. No. 399,622 9 Claims. (Cl. 122-406) The present invention relates generally to fluid heaters, and more particularly to multiple-pass water heaters in which the water passes in opposite directions across the heater through heat-exchange tubes therein.

In water heaters, particularly of the continuous flow type as opposed to storage type heaters in which fluid contained in a storage tank is recirculated through the heater, two conflicting operating characteristics are encountered. In the first place the inlet water is normally at a temperature below the dew point of the combustion gases in the heater so that condensate forms on the outer surface of the heat-exchange tubes for a substantial length adjacent to the water inlet. The low temperature of the heatexchange surfaces also causes sooting and the soot and condensate mixture drips from the heat-exchange tubes to cause corrosion within the fire box and plugging of the burner orifices beneath the cold portions of the tubes. To shorten the length of tube on which such condensate and sooting form, it is desired that the flow of the cold water through the inlet portions of the heat-exchange tubes be slow so that the water will be brought up above the dew point temperature in a minimum length of flow within the tubes.

However, as the water temperature increases, scaling and the deposit of minerals from the water increases and after the water is warmed, it is desired that the rate of flow be increased to keep the interior surfaces of the heatexchange tubes where the water is hot clean and to prevent scaling therein. Therefore, it is desired that the flow through the heat-exchange tubes be slow while the water is cold to limit sooting and condensate on the outside of the tubes, whereas fast flow is desired when the Water is hot to keep the interior of the heat-exchange tubes clean and prevent scaling. These two operating characteristics are therefore mutually conflicting and in the past it was necessary to strike a compromise between the desired slow flow while cold and the fast flow while hot so that the water through the heat-exchange tubes flowed at an intermediate rate which was not the optimum for either operating characteristic.

According to the present invention, a multiple-pass heater is employed in which slow flow of water is maintained through the cold heat-exchange passes adjacent to the water inlet, while fast flow is secured through the hot heat-exchange passes of the heater adjacent the outlet thereof. This variation in flow rate is secured by increasing the volume of water flowing through the hot passes over that flowing through the cold passes, and this is accomplishedby by-passing a portion of the total volume of water flowing through the heater about the cold passes adjacent the heater inlet. This by-passed water is mixed with heated water as it leaves the inlet heatexchange passes to pass thereafter the total flow only through the heat-exchange passes adjacent the heater outlet.

Where the Water pressure at the heater inlet is substantially constant, the by-pass around the cold heat-exchange passes can be a fixed passage which thereby by-passes a substantially constant proportion of the total flow through the heater. On the other hand, Where the water pressure at the inlet to the heat exchanger may vary, the by-pass passage around the cold heat-exchange passes may be variable in size and controlled, for example, by a thermal actuator responsive to water temperature either at the heater inlet or at the outlet from the cold heat-exchange passes, the latter construction being specifically illustrated and described herein.

To maintain the water pressure at the inlet to the heat exchanger substantially constant despite variations in the supply pressure, the primary flow regulator described and claimed in Miller Patent No. 3,134,366, granted May 26, 1964, for Flow Regulator for a Heater may be used. In this patent there is described and claimed a flow regulator for a water heater which compensates for variations in supply pressure by controllably lay-passing a portion of the flow directly from the heater inlet to the heater outlet, across all of the heat-exchange tubes. With the flow regulator of the Miller patent, the water pressure at the inlet to the heat exchanger is maintained relatively constant and when used with this arrangement the fixed passage bypassing only the cold heat-exchange passes becomes practical even where the supply pressure is variable; The combination of the full by-pass for controlling the over-all flow through the heat exchanger with the partial by-pass for only the cold heat-exchange passes is an important feature of the present invention.

It is therefore an object of the present invention to provide an improved water heater having multiple heatexchange passes with different rates of flow of the Water in the cold and hot heat-exchange passes.

Another object of this invention is the provision of an improved water heater having multiple heat-exchange passes in which only a portion of the total flow through the heater is passed through the cold heat-exchange passes, while the total flow is passed through the hot heatexchange passes, thereby increasing the rate of flow through. the hot heat-exchange passes.

A further object of this invention is the provision of an improved water heater having multiple heat-exchange passes in which a portion of the total water flowing through the heater is by-pa-ssed about only the cold heatexchange passes of the heater.

A still further object of this invention is the provision of an improved water heater having multiple heat-exchange passes in which a by-pass passage is provided around only the heat-exchange passes adjacent the inlet to the heater and in which the by-pass passage is controlled by a thermal actuator to vary the portion of water which is by-passed.

Another object of this invention is the provision of an improved water heater in accordance with any of the foregoing objects in which there is provided a by-pass passage directly between the inlet and outlet to the heater to maintain the water pressure at the inlet to the heat-exchange passes at a substantially constant value.

Other objects and features of the invention will be readily apparent to those skilled in the art from the following specification and the appended drawing, in which:

FIGURE 1 is a perspective view, with portions broken away, of a water heater according to the present invention;

FIGURE 2 is a partial horizontal sectional view showing the headers and heat-exchange tubes providing the multiple passes across the heater; and

FIGURE 3 is a detail sectional view showing the thermally controlled by-pass passages.

The form of water heater selected for specific illustration and description herein embodies a firebox 11 of sheet metal and an outer sheet metal covering 12', between which is an insulating layer 13 of rock wool or the like. In the bottom of the firebox 11 are disposed a series of burners 14 fed from a fuel line 15 through a control valve 16, a pressure regulator 17 and a solenoid control 18. A conventional safety pilot light and control are indicated at 19.

The water heater selected for illustration is of the multiple-tube, multiple-pass type, employing an inlet-out- 3 let manifold or header 21 at the front of the heater and a pass connecting manifold or header 22 at the back of the heater. Between the manifolds 21 and 22 extend heat-exchange tubes 23, shown as eight in number fora four-pass heater with the heat-exchanger tubes paired in each pass. It will be understood that a single or more than two heat-exchange tubes may be used in each pass and two or any greater number of passes may be used within the spirit of the present invention.

The heat-exchange tubes 23 have fins integrally mounted on their exterior surfaces to augment the heat-transfer area and are disposed in the firebox 11 above the burners 14. Bafiles 24 may be placed above the heatexchange tubes 23 as disclosed in the co-pending application of Avy L. Miller, Serial No. 214,156 filed July 20, 1962 for Fluid Heater, now Patent No. 3,160,145, granted December 8, 1964. Above the heat-exchange tubes 23 a hood 25 collects the products of combustion and directs them to the flue 26.

The heat-exchange tubes 23 are arranged in pairs in each pass across the heater, a pair 27 constituting the first pass through the heater from front to back, a pair 28 constituting the second pass across the heater from back to front, a pair 29 constituting the third pass across the heater from front to back, and a pair 30 constituting the fourth pass across the heater from back to front.

The back manifold 22 includes a structural mounting plate 31 in which are sealably mounted the rear ends of the heat-exchange tubes 23. Mounted on the plate 31 and extending across the heat-exchange tubes is a panshaped manifold member 32 having a wall 33 therein dividing its interior into two chambers 34 and 35. The chamber 34 connects the downstream end of the first pass across the heater to the upstream end of the second pass across the heater.

The front manifold 21 includes a structural mounting plate 36 in which the forward ends of the heat-exchange tubes 23 are sealably mounted. Attached to the mounting plate 36 is a pan-shaped manifold member 37 having an interior wall 38 defining an inlet chamber 39. A boss 41 extends outwardly from the manifold 21 and has a bore 42 therethrough communicating with the inlet chamber 39 and threaded to receive an inlet pipe 43. An integral partition Wall 44 further divides the interior of the manifold member 37 into chambers 45 and 46. A boss 47 extends outwardly from the manifold 21 and has a bore 48 communicating with the chamber 46 and threaded to receive an outlet pipe 49.

The inlet chamber 39 communicates directly with the inlet ends of the pair of heat-exchange tubes 27 constituting the first pass across the heater. The chamber 45 connects the downstream ends of the second pass heat-exchange tubes with the upstream ends of the third pass heat-exchange tubes. The outlet chamber 46 communicates with the downstream ends of the fourth pass heat-- exchange tubes.

The wall 38 is provided with a by-pass passage 51 therethrough to interconnect the chamber 39 and 45 and thereby provide a by-pass across the first two passes across the heater represented by the heat-exchange tube pairs 27 and 28. The passage 51 may be defined by a removable bushing 52 whereby the size of the passage and the amount of water diverted therethrough may be readily changed by selecting bushings with differing internal bores. In a two-pass heater where the heat-exchange pairs 29 and 30 would not be used, the passage 51 could constitute an exterior tube interconnecting the chambers 39 and 34, thereby by-passing only the first pass across the heater. However, for simplicity of construction and to avoid this piping, a four-pass heater is more readily adapted to the invention.

To incorporate the flow regulator of Miller Patent No. 3,134,366, the wall 38 is also provided with openings 53 intercommunicating the chambers 39 and 46 to thereby by-pass'theentire heat exchanger and divert water flow illustrated in FIGURE 3.

directly from the inlet pipe 43 to the outlet pipe 49. The openings 53 are adjustably closed by a valve plate 54 i biased toward the wall 38 by a spring 55 mounted over a spring guide pin 56 adjustabljy mounted by a nut 58 in a spider 57 forming an integral part of the Wall 38 and providing the openings 53. As taught in Patent No. 3 ,134,366, the control by-pass provided by the openings 53 and the spring biased valve plate 54 regulates the flow through 1 the heat exchanger of the heater to be independent of when the filter is clean and the supply pressure high, the

by-pass passage will gradually close as the filter clogs and thereby keep the pressure in chamber 39 and the flow through the heat exchanger substantially constant. With the pressure within chamber 39 maintained substantially constant, there will be a substantially constant volume of water diverted through the by-pass passage 51 and about the cold heat-exchange passes through the heater.

As explained in Miller Patent No. 3,134,366, the valve plate 54 may be controlled by a thermal actuator instead of 'by the spring 55, with the thermal actuator responding to the temperature of the water in the outlet chamber 46.

It will, of course, be understood that in systems in which the pressure supplied by the inlet pipe 43 remains substantially constant, the flow regulator provided by the bypass passages 53 and valve plate 54 may be entirely omitted, since its only purpose is to compensate for variations in supply pressure.

The thermal-actuator-controlled, partial by pass passage about the cold heat-exchange passes across the heater is This thermally controlled, partial by-pass may be used with the full by-pass flow regulator of Patent No. 3,134,366, but is illustrated alone, and is effective whether or not the inlet pressure to the heat exchanger varies. This modification will also compensate for variations in the temperature of the water at the inlet, since it is concerned solely with the temperature of the water leaving the cold heat-exchange passes and will there-.

fore compensate to some extent for variations in both the pressure and temperature of the inlet'water.

As specifically illustrated in FIGURE 3, the manifold member 37 is replaced by a manifold member 37A which is identical therewith except that the openings 53 and the control elements 54 through 58 are omitted. The internal wall 38A which defines the inlet chamber 39 is provided with a by-pass passage 61 between the chambers 39 and 45 which performs the general function of the passage 51, but the flow through which is controlled by a valve plate 62. The valve plate 62 is pivotally mounted at 63 above a platform 64 serving as a baflle to initially separate the flow through the passage 61 from the heated water flowing from the second pass heat-exchange tubes 28. An operating arm 65 is connected to the valve plate,

62 and extends through an opening in the platform 64 to support a thermal actuator 66 in position to be responsive to the heated water emerging from the heat-exchange tubes 28. The thermal actuator 66 includes a movable stem 68 which bears against the Wall 38A to effect movement of the actuator 66, arm 65 and valve plate 62 upon expansion and contraction of the actuator with a change in the temperature of the water emerging from the heat-exchange tubes 28.

The operation of the modification of FIGURE, 3 is such that as the water emerging from the second pass provided by the heat-exchange tube pair 28 heats up, the

thermal actuator 66 expands to throttle the passage 61 and thereby force more water to pass through the cold heatexchange passes, the increased speed of passage operating to lower the temperature of the water emerging from the second pass, since the heat input to the heater from the burners 14 is substantially constant. Conversely, if the water emerging from the second heat-exchange pass becomes colder, the actuator 66 contracts and the valve plate 62 is moved to further open the passage 61 whereby more water is diverted around the cold heat-exchange passes. This slows up the flow therethrough so that more heat is imparted to the Water therein and the temperature of the water emerging from the second pass tubes 28 will increase. It will be seen that this action regulates the bypass flow to a substantially constant temperature of water emerging from the second heat-exchange pass, regardless of the pressure and temperature of the water at the inlet.

According to the present invention, it is no longer necessary to strike a full compromise between the desired operation of slow flow through the cold heater passes and fast flow through the hot heater passes. These desired conditions are more nearly approximated by diverting a portion of the flow through the heater about only the cold heat-exchange passes thereof, whereby more Water flows through the hot heat-exchange passes at a necessarily higher rate of flow than through the cold heat-exchange passes. Where there is a substantially constant inlet pressure, a fixed opening by-pass passage may be efiectively provided about the cold heat-exchange passes. The invention further includes in combination a flow regulator constituted by a built-in automatic by pass about the entire heat exchanger whereby variations in the supply pressure are substantially compensated to maintain the inlet to the heat exchanger at relatively constant pressure.

In another embodiment of the invention the by-pass passage about only the cold heat-exchange passes of the heater is controlled in size by a thermal actuator so as to more truly approach the desired operating characteristics. The thermal actuator may be made responsive to the water temperature at any portion in the heater, but preferably to the temperature of the water emerging from the heat-exchange passes about which the Water is by-passed and prior to its mixing with the diverted water.

\Vhile certain preferred embodiments of our invention have been specifically illustrated and described, it will be understood that our invention is not limited thereto as many variations will be apparent to those skilled in the art, and the invention is to be given its broadest interpretation within the terms of the following claims.

We claim:

1. A water heater comprising: an inlet for cold water; an outlet for heated water; heat-exchange means extending between said inlet and outlet for the passage therethrough of water to be heated; means for burning fuel and directing the products of combustion over said heatexchange means; and bypass means for diverting a portion of the water entering said heater around a portion only of said heat-exchange means adjacent the inlet thereto whereby the total flow of water passing through the heat-exchange means occurs only in the hotter portion thereof whereby to create a difference in the rate of flow of water through the hot and cold portions of the heat-exchange means.

2. A water heater comprising: an inlet for cold water; an outlet for heated water; heat-exchange means extending between said inlet and outlet for the passage therethrough of water to be heated; means for burning fuel and directing the products of combusition over said heatexchange means; -by-pass means for diverting a portion of the water entering said heater around a portion only of said heat-exchange means adjacent the inlet thereto whereby the total flow of water passing through the heat-exchange means occurs only in the hotter portion thereof whereby to create a diflerence in the rate of flow of Water through the hot and cold portions of the heatexchange means; and a thermal actuator responsive to the temperature of the water at a predetermined point for varying the flow through the bypass means to secure a desired relative flow in the hot and cold portions of the heat-exchange means.

3. A Water heater comprising: an inlet for cold water; an outlet for heated water; heat-exchange means extending between said inlet and outlet for the passage therethrough of water to be heated; means for burning fuel and directing the products of combustion over said heat exchange means; by-pass means for diverting a portion of the water entering said heater around a portion only of said heat-exchange means adjacent the inlet thereto whereby the total flow of water passing through the heatexchange means occurs only in the hotter portion thereof whereby to create a difference in the rate of flow of water through the hot and cold portions of the heat-exchange means; and a flow regulator interconnecting said inlet and outlet to compensate for variations in pressure of the water supplied to the inlet to maintain the pressure at the entrance to the heat-exchange means and the flows therethrough substantially constant.

4. A water heater comprising: an inlet for cold water; an outlet for heated water; heat-exchange tubes extending across the heater and communicating with said inlet and outlet, said inlet and outlet being located on the same side of the heater; means at the side of the heater opposite the inlet and outlet for connecting said heatexchange tubes to secure a plurality of passes of the water flowing therethrough across the heater; means for burning fuel and passing the products of combustion into contact with the exterior of said heat-exchange tubes; and a by-pass passage interconnecting the inlet to the first heatexchange tube pass to the inlet to a later heat-exchange tube pass whereby to secure a faster rate of flow of the Water through the later and warmer heat-exchange pass of the heater.

5. A water heater comprising:an inlet for cold water; an outlet for heated water; heat-exchange tubes extending across the heater and communicating with said inlet and outlet, said inlet and outlet being located on the same side of the heater; means at the side of the heater opposite the inlet and outlet for connecting said heat-exchange tubes to secure a plurality of passes of the water flowing therethrough across .the heater; means for burning fuel and passing the products of combustion into contact with the exterior of said heat-exchange tubes; by-pass passage interconnecting the inlet to the first heat-exchange tube pass to the inlet to a later heat-exchange tube pass whereby to secure a faster rate of flow of the water through the later and warmer heat-exchange pass of the heater, said by-pass passage being of fixed size to divert a predetermined proportion of the water entering the heater about the cold heat-exchange pass; and a flow regulator interconnecting said inlet and outlet for by-passing variable amounts of water across the entire heat-exchanger in accordance with variations in the supply pressure whereby to regulate the water pressure adjacent the entrance to the heat exchanger against wide variations.

6. A water heater comprising: an inlet for cold water; an outlet for heated Water; heat-exchange tubes extending across the heater and communicating with said inlet and outlet, said inlet and outlet being located on the same side of the heater; means at the side of the heater opposite the inlet and outlet for connecting said heatexchange tubes to secure a plurality of passes of the water flowing therethrough across the heater; means for burning fuel and passing the products of combustion into contact with the exterior of said heat-exchange tubes; a by-pass passage interconnecting the inlet to the first heat-exchange tube pass to the inlet to a later heatexchange tube pass whereby to secure a faster rate of flow of the water through the later and warmer heatexchange pass of the heater; and a thermal actuator responsive to the temperature of the water in the heater 7 just prior to its re-mixture with the water diverted through the by-pass passage for varying the flow through said by-pass passage to maintain a desired differential between the rates of flow through the hot and cold heat-exchange passes.

7. A water heater comprising: an inlet for cold water; an outlet for heated water, said inlet and outlet being located on the same side of the heater; a manifold at said heater side providing an inlet chamber connected to said cold water inlet, an outlet chamber connected to said heated water outlet, and an intermediate chamber; heatexchange tubes extending across the heater from said side to the opposite side thereof, and being at least four in number to provide four passes for water flow across the heater, the heat-exchange tube of the first pass being connected to said inlet chamber, the heat-exchange tubes of the second and third passes being connected to said intermediate chamber, and the heat-exchange tube of the fourth pass being connected to said outlet chamber; a manifold at said opposite side of the heater providing a pair of chambers including a first chamber interconnecting the heat-exchange tubes of the first and second passes and a second chamber interconnecting the heat-exchange tubes of the third and fourth passes; means for burning fuel and directing products of combustion across the outside of said heat-exchange tubes; and a by-pass passage interconnecting said inlet chamber to said intermediate chamber to divert a portion of the water passing through the heater around said first and second passes whereby to pass a greater volume of water at a faster rate of flow through the third and fourth passes of the heater than passes through the first and second passes thereof.

8. A water heater comprising: an inlet for cold water; an outlet for heated water, said inlet and outlet being located on the same side of the heater; a manifold at said heater side providing an inlet chamber connected to said cold water inlet, an outlet chamber connected to said heated water outlet, and an intermediate chamber; heatexchange tubes extending across the heater from said side to the opposite side thereof, and being at least four in number to provide four passes for water flow across the heater, the heat-exchange tube of the first pass being connected to said inlet chamber, the heat-exchange tubes of the second and third passes being connected to said intermediate chamber, and the heat-exchange tube of the fourth pass being connected to said outlet chamber; a manifold at said opposite side of the heater providing a pair of chambers including a first hamber interconnecting the heat-exchange tubes of the first and second passes and a second chamber interconnecting the heat-exchange tubes of the third and fourth passes; means for burning fuel and directing products of combustion across the outside of said heatexchange tubes; a by-pass passage interconnecting said inlet chamber to said intermediate chamber to divert a 8 portion of the water passing through the heater around said first and second passes whereby to pass a greater volume of water at a faster rate of fiow through the third and fourth passes of the heater than passes through the first and second passes thereof, said by-pass passage being of fixed size to divide the water flowing through the passage and through the first and second heat-exchange passes in predetermined proportions; and flow regulator means interconnecting said inlet and outlet chambers and operating to maintain substantially constant volumes and rates of flow through the heat-exchange passes.

9. A water heater comprising: an inlet for cold water; an outlet for heated water, said inlet and outlet being located on the same side of the heater; a manifold at said heater side providing an inlet chamber connected to said cold water inlet, an outlet chamber connected to said heated water outlet, and an intermediate chamber; heatexchange tubes extending across the heater from said side to the opposite side thereof, and being at least four in number to provide four passes for water flow across the heater, the heat-exchange tube of the first pass being connected to said inlet chamber, the heat-exchange tubes of the second and third passes being connected to said intermediate chamber, and the heat-exchange tube of the fourth,

pass being connected to said outlet chamber; a manifold at said opposite side of the heater providing a pair of chambers including a first chamber interconnecting the heat-exchange tubes of the first and second passes and a second chamber interconnecting the heat-exchange tubes of the third and fourth passes; means for burning fuel and directing the products of combustion across the outside of said heat-exchange tubes; a by-pass passage interconnecting said inlet chamber to said intermediate chamber to I divert a portion of the water passing through the heater around said first and second passes whereby to pass a greater volume of water at a faster rate of How through the third and fourth passes of the heater than passes through the first and second passes thereof; and a thermal actuator responsive to the temperature of the water leaving said second heat-exchange pass for varying the eifective size of said by-pass passage and the amount of water diverted around said first and second heat-exchange passes.

References Cited by the Examiner UNITED STATES PATENTS 30,326 10/1860 Johnson 122-406 2,055,784 9/ 1936 Cilark 122406 X 3,134,366 5/1964 Miller l22407 3,203,404 8/1965 Miller 122-236 FREDERICK L. MATTESON, JR., Primary Examiner. ROBERT A. DUA, Assistant Examiner. 

1. A WATER HEATER COMPRISING: AN INLET FOR COLD WATER; AN OUTLET FOR HEATED WATER; HEAT EXCHANGE MEANS EXTENDING BETWEEN SAID INLET AND OUTLET FOR THE PASSAGE THERETHROUGH OF WATER TO BE HEATED; MEANS FOR BURNING FUEL AND DIRECTING THE PRODUCTS OF COMBUSTION OVER SAID HEATEXCHANGE MEANS; AND BY-PASS MEANS FOR DIVERTING A PORTION OF THE WATER ENTERING SAID HEATER AROUND A PORTION ONLY OF SAID HEAT-EXCHANGE MEANS ADJACENT THE INLET THERETO WHEREBY THE TOTAL FLOW OF WATER PASSING THROUGH THE HEAT-EXCHANGE MEANS OCCURS ONLY IN THE HOTTER PORTION THEREOF WHEREBY TO CREATE A DIFFERENCE IN THE RATE OF FLOW OF WATER THROUGH THE HOT AND COLD PORTIONS OF THE HEAT-EXCHANGE MEANS. 